Hydraulic fluid controls can be found in a variety of automotive applications such as automatic speed change transmissions as well as others. In these applications, it is often desirable to control the pressure of the hydraulic fluid.
In the specific context of an automatic speed change power transmission, it is known to use electronic transmission control units that are configured to generate electrical signals that control solenoids resulting in the control of fluid flow as well as the pressure in a hydraulic fluid line. As known, the pressure in a hydraulic fluid line can be used to control various other elements in an automatic transmission system including for example a hydraulically-actuated clutch for the engagement of individual gears. By engaging various combinations of gears (e.g., planetary gears in a planetary gear transmission), an automatic transmission system accomplishes the same task as the shifting of gears in a manual transmission. Hydraulically-actuated clutches that are found in transmissions are typically used for engaging a pair of gears (e.g., a pair of rotating members, or alternatively, one rotating member and one non-rotating member) together such that when the clutch is applied, torque can be transmitted from one shaft to the other. Shift changes may also include switching three or more clutches on occasion for certain types of shifts, and herein references to two clutch type shifts could also include the multiple shifts.
An important operating aspect of a hydraulically operated clutch relates to the pressure build-up of the applied hydraulic fluid. In general, fluid flow at a certain applied pressure is sought to be controlled and varied to apply the clutch in order to obtain a desired engagement characteristic, principally with respect to timing and smoothness. It should be appreciated that if the timing of the engagement of one gear with the disengagement of another gear is not coordinately properly, overall shift performance may suffer. It is thus desirable and known in the art to control the clutch pressure. It is known to provide a linear solenoid to control the hydraulic fluid pressure to apply and/or release the clutch. In a linear solenoid, the amount of fluid at a controlled pressure can be varied by changing a solenoid control current.
Such electro-hydraulic (EH) systems are complex, and even generally similar EH systems (e.g., alternate automatic transmission hardware platforms) have a response that is different from system-to-system, and which is dependent on the particular EH plant characteristics. For example, each EH system may have a different and unique electrical drive circuit for producing a required solenoid control current. Moreover, each may have a different and unique linear solenoid that is being driven. An overall controller may be provided for use across a variety of such similar platforms, and conventionally may employ a proportional-integral (PI) control strategy for controlling the step response of the system. It is known to provide such a generic PI controller using gain constants that are selected to give a good overall response, but under some circumstances may result in instability and/or a slow response. Inherent in the conventional approach is a compromise regarding the overall range of operating conditions expected to be encountered as well as variation in the actuator dynamics across various platforms.
U.S. Pat. No. 6,588,394 entitled “MODEL-BASED CONTROL OF A SOLENOID-OPERATED HYDRAULIC ACTUATOR FOR ENGINE CYLINDER DEACTIVATION” issued to Zheng (“Zheng”), owned by the common assignee of the present invention and incorporated herein by reference in its entirety, discloses a model that characterizes a solenoid valve, which is used in an open loop context to calculate a solenoid plunger response time, which in turn is used in an overall timing calculation. The Zheng reference, however, does not teach the use of the solenoid valve model for dynamically adjusting control gains used to control the solenoid.
There is therefore a need for a system and method for providing a dynamic solenoid response adjust control that minimizes or eliminates one or more of the problems described above.